Sound reproducing system



Oct. 15, 1935. E. w. KE LLOGG 2,017,153

SOUND REPRODUCING SYSTEM File'd NOV. 10. 1932 @7 1 I v 1 A -5 f INVENTORI 'Edtblltd WKJellagg 5 ATTORNEY Patented Oct. 15, 1935 UNITED STATES SOUND REPRODUCING SYSTEM Edward W. Kellogg, Moorestown, N. J., assignor to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application November 10, 1932, Serial No. 641,955

16 Claims.

This invention relates to a method of and system for producing natural reverberation effects in auditoria, and more particularly to a method of and system for producing such effects in theatres in connection with reproduced sound.

It is well known that musical effects resulting from reverberation give greater pleasure to listeners than the same music produced, for exam.- ple, out of doors. It is also well known that if music is produced in rooms with too much reverberation the sounds may develop to such a degree as to become confusing to the listener, while music reproduced in rooms with too little reverberation has usually been criticized as being dull-. A certain amount of reverberation is,

however, necessary in order to produce a pleasing effect, and this applies to reproduced sound as well as to originally produced sound.

Not only is the correct amount of reverberation important for the maximum enjoyment of music, but, in our normal experience, practically all sounds are followed by more or less echoes and reverberation which serve to convey an impression in regard to our surroundings. In the reproduction of sound, especially in connection with motion pictures, it is desired to give the auditor as complete an illusion as possible of being actually present at the scene of action. To this end, not only must the initial sound be reproduced with minimum distortion, but the reverberation which follows must simulate in all respects the reverberation which the surroundings portrayed would cause. The simulation of the original reverberation depends upon the duplication, of the proper duration and quality, of the echoes and 'reverberant sound, and also upon their direction as sensed by the listener.

The most approved present practice, in co 'nection with sound pictures reproduced in thea- 40 tres, is to supply whatever reverberation effects are necessary in the record and to reduce reverberation in the auditorium or theatre to a relatively small value.- This is practically necessary because any reverberation in the theatre would 5 be a nearly constant factor and couldnot bemade to change with the nature of the scene being portrayed. The great fault with the present system, however, is that all of the reverberation comes from the loudspeaker or speakers mounted in the U0 vicinity of the screen, and an unnatural effect is produced when all of the reverberation comes from the same direction as the initial sound.

If, for example, one stands outside of a room in which "a band is playing and the music comes to him through an open window, he'hears reverberation from the same direction as the music, and the effect is very different from that which he gets when he is in the room. Having the reverberation and the original sound all come from the same loudspeaker gives the listener an im- 5 pression such as just described, namely, that of hearing the sound from outside through an opening. One's ability to concentrate on sound coming from a certain direction is of such importance that it is not possible to give a satisfactory imi- 10 tation of a sound coming from one direction by means of a sound which comes from some other direction.

It has been found necessary, in the recording of sound for motion pictures in the system hith- 15 erto generally employed, to provide somewhat. less reverberation in the recording studio or sound stage than would normally exist in the surroundings portrayed, for the reason that a given amount of reverberation seems like more when 20 it comes from the same direction as the original sound than it does when coming from other diducing such natural effects. 35

Another object of my invention is to provide a method of and system for producing reverberation effects in an auditorium which will simulate, as nearly as possible, the reverberant condition which exists at 'the place where the original 40 sound is produced.

Still another object of my invention is to provide a system for producing natural reverberation effects by means, of which substantially non- -reverberant sound maybe reproduced simultaneuosly with, although independently of, thesame sound with reverberation.

In some cases it may be desired to reproduce sounds with practically no reverberation as, for example, when a close up is being shown, the performers being either in a small room or out of doors. For portraying such scenes, all reverberation in the theatre is detrimental, and, in addition to providing sound. absorption, it is helpful to employ a directive loudspeaker, since this should be well diffused, for which purpose nondirective loudspeakers have an advantage. Accbrdingly, it is a further object of my invention to provide a system for producing natural rever beration efiects by means of which substantially non-reverberant sound may be reproduced directively whilethe same sound with reverberation may be reproduced simultaneously but non-directively.

Still a further object of my invention is to provide a record of substantially non-reverberant sound and another and independent record of the same sound with reverberation, which record may be employed as a part of a system according to my invention.

A fur her object of my invention is to provide a system for producing natural reverberation effects which is simple in construction, inexpensive of manufacture and installation, and efiicient in In accordance with my invention, I provide, in

addition to the usual loudspeaker or speakers located behind the screen, a plurality of loudspeakers scattered about the theatre. Sound recorded with minimum reverberation is then supplied from the loudspeakers located behind the screen, while the scattered loudspeakers supply sound carrying whatever reverberation is desired. I

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation,- together with additional objects and advantages thereof, will best be understood from the following description of several embodiments, when read in connection with the accompanying drawing, in which Figure l is a diagrammatic view illustrating one system for carrying out my invention,

Figure 2 is a diagrammatic view illustrating a second system for carrying out my invention, and

Figure 3 is a diagrammatic view illustrating a third. and preferred, system for carrying out my invention.

Referring to the drawing, wherein similar reference characters indicate corresponding parts throughout, l represents an auditorium, such as a theatre, provided with the usual seats 2, stage I,

and screen I. A sound reproducing machine 5, energized by a sound record on' which sound with substantially no reverberation :has been recorded;

, actuates a loudspeaker I which is located behind the screen I and a second loudspeaker I located within a resonant chamber I. It will thus be seen that the loudspeaker 6 reproduces the sound as recorded, that is, with practically no reverberation; at a point adjacent the screen ,4 where there is reproduced the action with which the sound is synchronized, while the loudspeaker I reproduces the same sound within -the resonant chamber 0. r

The sound reproduced by the loudspeaker I is permitted toreverberate within the chamber 8,

the reverberated sound being picked up by a microphone 9, also located within the chamber I, amplified by an amplifier ll, and reproduced by anumber of loudspeakers ll distributed over the auditorium I. A volume control I! may, if desired, be included in the circuit to the loudspeaker l to regulate the amount of reverberation introduced into the auditorium. Control of the amount of reverberation in the. auditorium may 2,017,158 has the efiect of minimizing the ratio of auditoalso be had by adjustment of the volume control l3 in the output circuit of the amplifier Ill. The period of reverberation in the chamber 8 may be controlled by providing one or more adjustable vents, or by means of adjustable panels ll of absorbing material. Since the loudspeakers H are distributed about the auditorium and are pointed in a number of diiierent directions, the reverberant sound reproduced by these speakers will be projected in a number of different directions and will reach an auditor in the auditorium i from many directions. The substantially nonreverberant sound from the loudspeaker 5, however, will reach the auditor from but one direction. Thus, the condition for natural effects is realized and the inipression upon the auditor is pleasing and more realistic than is possible with systems ordinarily employed.

In the modification of my invention illustrated in Fig. 2, the loudspeaker 6, located behind the screen 4, is actuated by the reproducing machine 5 as in the modificationillustrated in Fig. 1. However, in order to ,cut down the number of loudspeakers required at I I as well as the microphone 9, amplifier III and control iii, a number of resonant chambers, such, for example, as the galleries 20, 2ll, may be provided adjacent to the auditorium I. The reproducing machine would then actuate several loudspeakers la, la, one in each resonant gallery 20, and the sound emitted by the loudspeakers Ia and made reverberant by the chambers 20 would reach'the audience through the openings 2! connecting the resonant chambers 20 with the auditorium l. The chambers 20 may, if desired, be provided with baffles 22, pivoted at 23, whereby to adjust the amount of absorption of the sound in the chambers 20.

While the two modifications of my invention just previously described fulfill the conditions necessary to cause the reverberation to reach the auditor from the desired directions, the principal objection thereto tor-motion picture purposes is that too much reliance would have to be placed upon the judgment of the operator or projectionist, and the nature of the reverberation (rate of decay and selective absorption of high or low frequencies) could not be as completely controlled as could be done if reverberation oi the desired character were produced and recorded at the time of. the original action. A system such as illustratedin Fig. 3 and in which are employed two sound records and separate sound channels;

picked up by the microphone 3|, it may be of a type which is insensitive to sound coming from certain directions, and the directiw'ty of .the microphone may be further augmented by means of a shield]! which shields it from sound coming from directions other than the actor or sound source S, so that the sound picked up by the microphone II will have as little reverberation as possible. Theelectrical pulsations or waves produced in the circuit of the microphone 31 by the sound picked up thereby are amplified by an amplifierll the output of which may, if desired, be

- 'verberation. To further reduce the reverberation desired, by a gain contr controlled by a gain control 36, and transmitted to a recorder 38 which records a record 40 of substantially non-reverberant sound.

A second microphone 33 is.so placed in the chamber 3| as to pick up reverberation of the desired quality. In order that the sound picked up by microphone 33 may consist almost entirely of reverberation with comparatively little of the initial sound, it would normally be placed at some distance from the source S, and it might be desirable to employ a rective microphone here also. The sound picked p by the microphone 33 is transformed thereby into electrical waves which are amplified by an am lifier 35, controlled,.if 31, and transmitted to a recorder 39 which records a record 4| of reverberant sound. The records 40 and 4| are si multaneously recorded and, of course, may represent the same or different sounds, but in any event, the record 40 is representative of substantially non-reverberant sound and the record 4| of reverberant sound.

The record R. with its two sound tracks 40 and 4| may then be employed to energize, through one channel, the loudspeaker 6, and, through another channel, the loudspeakers H. For this purpose, a reproducer 42 may be utilized to scan the record 40, the output therefrom being amplifled by an amplifier 44 -and transmitted to the loudspeaker, 6, a suitable control 46 controlling the output of the amplifier 44. Asimilar reproducer 43 scans the record 4|, and actuates an amplifier 45 of which the output, controlled by a control 41, is employed to energize the loudspeakers whereby the reverberantsound is radiated into the auditorium While I have described the modification of Fig. 3 as applied to a system wherein both the records 40 and 4| are preferably applied to but one record medium or film R, it should be understood that the records 40 and 4| may, if desired, be

made on separate record media and that any satisfactory system may be employed for either or both the records. For example, both records might be made on either film or on discs, or one record might be made on film and the other on disc. The last mentioned system is especially adaptable to existing installations, many of which are already equipp d so that a film and a disc record can be played simultaneously.

'1 also wish it to be understood that theleudspeaker isreferred to herein as "adjacent to the screen if it is located so as to cause the sound to come from the scene-of action, while the term remote is applied if the loudspeaker is placed so as to cause the sound to come from a different direction.

Furthermore, although I have shown and described herein several embodiments of my invention, it will be obvious to those skilled in the art that many othermodifications thereof are postion effects in an auditorium in connection with reproduced sound which comprises reproducing sound with as little reverberation as possible at one point in the auditorium and simultaneously reproducing the same sound with reverberation at at least one other point in said auditorium.

2. The method of producing natural reverberation' efiects in an auditorium in connection with reproduced sound which comprises reproducing sound with as little reverberation as possible at one point in said auditorium and simultaneously reproducing the same sound with reverberation at a plurality of separated points in said auditorium, said non-reverberant sound being re,- produced. directively and said reverberant sound being reproduced nondirectively.

3. In the method of simultaneously reproduc ing synchronized sound and action in an auditorium, the step of producing natural reverberation effects in said auditorium which comprises reproducing with as little reverberation as possible sound corresponding to the action from a point adjacent that at which the action is reproduced, and simultaneously reproducing the same sound with reverberation from a plurality of other points in said auditorium.

4. In the method of reproducing action upon a screen in an auditorium and simultaneously reproducing sound to accompany said action, the step of producing natural reverberation effects in said auditorium which comprises reproducing with as little reverberation as possible sound accompanying the action from a point adjacent said screen, and simultaneously reproducing the same sound with reverberation from a. plurality of separated points in said auditorium, said non-reverberant sound being reproduced directively and said reverberant sound being reproduced nondirectively.

5. The method of producing natural reverbera-' tion effects in an auditorium in connection with reproduced sound which comprises recording sound with as little reverberation as possible upon a record blank through one channel, simultaneo through a channel terminating in one part of said auditorium, and simultaneously reproducing the ,same sound with reverberation through another channel terminating in another part of said auditorium. v

'7. The combination with an auditorium including a screen on which moving pictures may be projected or a sound reproducing system including a plurality of channels, one of said channels having an outlet adjacent said screen, the other of said channels having a plurality of outlets about the auditorium at points remote from said screen, and means in at least one of said channels for controlling the reverberation of the sound reproduced thereby.

8. The combination with an auditorium including a screen on which moving pictures may be projected of a sound reproducing system including a plurality of channels, one of said channels having an outlet adjacent saidscreen, the other of said channels having a plurality of outlets about the auditorium at points remote from said screen, and means in said other channel for controlling the reverberation of the sound reproduced thereby.

9. Thecombination with an auditorium of a sound reproducing system for reproducing sound 'from a record thereof recorded with substantially no reverberation, said system including a pluralchannel the sound recorded by said first record- I 11. The combination with an auditorium in,-'

cluding a screen on which moving pictures may be projected of a sound reproducing system for reproducing sound from a record thereof recorded with substantially no reverberation, said system including at least two channels one of which has an outlet adjacent said screen and the other of which has a plurality of outlets about said auditorium at points remote from said screen, and means in said latter channeLtor.

I imparting reverberation to the sound reproduced therethrough, said reverberation imparting means being adjustable.

12. The method of recording sound on and reproducing that sound mm a record medium which comprises producing electrical waves corresponding to said sound with as little reverberation as possible, transmitting said electrical waves to a recording device and recording said waves on said medium, simultaneously separately producing. electrical waves corresponding to said sound with reverberation, transmitting said latter waves to asecond recording device and recording saidlatter waves on said medium, reproducing in one ing device, and simultaneously reproducing, in

' another channel, thesound recorded by said second recording device.

. tions of the same sound with 7 same. or another record medium.

13. The method of recording sound on and reproducing that sound from a record medium which comprises producing electrical waves corresponding to said sound with as little reverberation as possible, transmitting said electrical waves to a recording device and recording said waves along one path on said medium, simultaneously separately producing electrical waves corresponding to said sound with reverberation, transmitting said latter waves to .a second recording device and recording said latter waves along another path on said medium, reproducing in one channel the sound recorded by said first recording device, and simultaneously reproducing, in

another channel, the sound recorded by said sec-' ond recording device.

14. In apparatus for recording sound, means for producing undulations oi! the sound with as little reverberation as possible, means for recording said undulations on a record medium, means for producing undulations or the same sound with reverberation, and means ior separately recording said lastnamed undulations upon the 15. In apparatus for recording sound, means for producing undulations oi the sound with as little reverberation as possible, means for recording said undulations on a record medium along one path thereon, means for producing undulareverberation, and means for recording said'last. named undulations upon the same record medium but along another path thereon. i

16. A sound record comprising a record medium having a plurality of records thereon, one oi. said records representing sounds recorded with as little reverberation as possible, and another of said records representing the same sound recorded with reverberation.

EDWARD w. Knuooo. w 

